Validity Study of Rough Surface Scattering Models

We present a study of the regions of accuracy of various rough surface scattering models including the physical optics approximation and the small perturbation method. The accuracy of the models is compared for surfaces with power law and Gaussian power spectra. RMS error values between the exact method of moments solution and the models are shown over the entire parameter space studies. Results of the study also demonstrate a linear relationship between the accuracy of the methods and the moments of the surfaces

High Planar Arrays and Array Feeds for Satellite Communications

Limited scan range beamsteering can serve as a cost-effective solution for three application scenarios in satellite communications. Two feasible technical paths to realize the function are discussed in this paper. The first one is to utilize a electronically steered array feed with a conventional parabolic reflector. By feeding the reflector with different weights across the array feed, the phase distribution on the dish aperture is continuously shifted leading to a steered beam. Acquisition and tracking functions can be realized economically by integrating a power detector based feedback system. A necessary calibration process is provided to ensure a correct indicator of signalto- noise ratio. One dimensional bemsteering was demonstrated experimentally and an improved two dimensional system is shown as well. The second path is to use a tile array with each tile consisting of a passive network fed subarray, which reduces the cost of active components significantly, at the expense of beamsteering range. The rule of the relationship between tile distance and element distance is discussed. Preliminary array factor analysis shows the sidelobe level of a uniformly excited array panel exceeds the regulatory pattern mask requirement

Improving Electromagnetic Bias Estimates

The derivation of an electromagnetic (EM) bias model that includes the physical optics scattering models and the non-Gaussian long wave surface statistics is presented. The final formulation of the model is expressed as a function of hydrodynamic modulation, surface skewness, and tilt modulation. Through the modulation transfer function, the hydrodynamic modulation coefficient is shown to be equivalent to the long wave RMS slope multiplied by a function of the short wave spectrum. With this result the normalized EM bias reduces to a function of long wave surface parameters with coefficients determined by properties of the short ocean waves. EM bias values are computed from the theory, using a realistic surface PSD, and compared with in situ bias measurements. The bias model is shown to be in excellent agreement with the measured values, and includes features of normalized bias not present in previous models

A Versatile Wireless Network Protocol for Spectrum Sharing with Passive Radio Services

With the proliferation of wideband active services in bands shared with passive receivers for remote sensing and radio astronomy, new methods are needed for deconflicting active and passive users. We have developed a technique for active/passive user coordination that is compatible with essentially any existing wireless communications protocol. The passive user transmits an on-off keying modulated signal that can be detected by active radios using simple channel power estimates. Using off-the-shelf WiFi and LoRa hardware and on a software defined radio implementation of LTE, we show that Dynamic Passive to Active Spectrum Sharing (DPASS) is effective on a wide range of frequencies and physical layer implementations. We validate the protocol using these three technologies by demonstrating that each device receives a DPASS packet and dynamically takes an appropriate spectrum coordination action, including shutting off transmissions or switching frequencies.Comment: 9 pages, 8 figure

Phased Array Feed Calibration, Beamforming and Imaging

Phased array feeds (PAFs) for reflector antennas offer the potential for increased reflector field of view and faster survey speeds. To address some of the development challenges that remain for scientifically useful PAFs, including calibration and beamforming algorithms, sensitivity optimization, and demonstration of wide field of view imaging, we report experimental results from a 19 element room temperature L-band PAF mounted on the Green Bank 20-Meter Telescope. Formed beams achieved an aperture efficiency of 69% and system noise temperature of 66 K. Radio camera images of several sky regions are presented. We investigate the noise performance and sensitivity of the system as a function of elevation angle with statistically optimal beamforming and demonstrate cancelation of radio frequency interference sources with adaptive spatial filtering.Comment: 19 pages, 13 figure

Performance of Polarimetric Beamformers for Phased Array Radio Telescopes

Abstract The results of four recently introduced beamforming schemes for phased array systems are discussed, each of which is capable to provide high sensitivity and accurate polarimetric performance of array-based radio telescopes. Ideally, a radio polarimeter should recover the actual polarization state of the celestial source, and thus compensate for unwanted polarization degradation effects which are intrinsic to the instrument. In this paper, we compare the proposed beamforming schemes through an example of a practical phased array system (APERTIF prototype) and demonstrate that the optimal beamformer, the max-SLNR beamformer, the eigenvector beamformer, and the bi-scalar beamformer are sensitivity equivalent but lead to different polarization state solutions, some of which are sub-optimal

Pan-Cancer Analysis of lncRNA Regulation Supports Their Targeting of Cancer Genes in Each Tumor Context

Long noncoding RNAs (lncRNAs) are commonly dys-regulated in tumors, but only a handful are known toplay pathophysiological roles in cancer. We inferredlncRNAs that dysregulate cancer pathways, onco-genes, and tumor suppressors (cancer genes) bymodeling their effects on the activity of transcriptionfactors, RNA-binding proteins, and microRNAs in5,185 TCGA tumors and 1,019 ENCODE assays.Our predictions included hundreds of candidateonco- and tumor-suppressor lncRNAs (cancerlncRNAs) whose somatic alterations account for thedysregulation of dozens of cancer genes and path-ways in each of 14 tumor contexts. To demonstrateproof of concept, we showed that perturbations tar-geting OIP5-AS1 (an inferred tumor suppressor) andTUG1 and WT1-AS (inferred onco-lncRNAs) dysre-gulated cancer genes and altered proliferation ofbreast and gynecologic cancer cells. Our analysis in-dicates that, although most lncRNAs are dysregu-lated in a tumor-specific manner, some, includingOIP5-AS1, TUG1, NEAT1, MEG3, and TSIX, synergis-tically dysregulate cancer pathways in multiple tumorcontexts

Pan-cancer Alterations of the MYC Oncogene and Its Proximal Network across the Cancer Genome Atlas

Although theMYConcogene has been implicated incancer, a systematic assessment of alterations ofMYC, related transcription factors, and co-regulatoryproteins, forming the proximal MYC network (PMN),across human cancers is lacking. Using computa-tional approaches, we define genomic and proteo-mic features associated with MYC and the PMNacross the 33 cancers of The Cancer Genome Atlas.Pan-cancer, 28% of all samples had at least one ofthe MYC paralogs amplified. In contrast, the MYCantagonists MGA and MNT were the most frequentlymutated or deleted members, proposing a roleas tumor suppressors.MYCalterations were mutu-ally exclusive withPIK3CA,PTEN,APC,orBRAFalterations, suggesting that MYC is a distinct onco-genic driver. Expression analysis revealed MYC-associated pathways in tumor subtypes, such asimmune response and growth factor signaling; chro-matin, translation, and DNA replication/repair wereconserved pan-cancer. This analysis reveals insightsinto MYC biology and is a reference for biomarkersand therapeutics for cancers with alterations ofMYC or the PMN

Genomic, Pathway Network, and Immunologic Features Distinguishing Squamous Carcinomas

This integrated, multiplatform PanCancer Atlas study co-mapped and identified distinguishing molecular features of squamous cell carcinomas (SCCs) from five sites associated with smokin

Spatial Organization and Molecular Correlation of Tumor-Infiltrating Lymphocytes Using Deep Learning on Pathology Images

Beyond sample curation and basic pathologic characterization, the digitized H&E-stained images of TCGA samples remain underutilized. To highlight this resource, we present mappings of tumorinfiltrating lymphocytes (TILs) based on H&E images from 13 TCGA tumor types. These TIL maps are derived through computational staining using a convolutional neural network trained to classify patches of images. Affinity propagation revealed local spatial structure in TIL patterns and correlation with overall survival. TIL map structural patterns were grouped using standard histopathological parameters. These patterns are enriched in particular T cell subpopulations derived from molecular measures. TIL densities and spatial structure were differentially enriched among tumor types, immune subtypes, and tumor molecular subtypes, implying that spatial infiltrate state could reflect particular tumor cell aberration states. Obtaining spatial lymphocytic patterns linked to the rich genomic characterization of TCGA samples demonstrates one use for the TCGA image archives with insights into the tumor-immune microenvironment